1. Field of the Invention
The present invention relates to patient interface devices for communicating a flow of gas with an airway of a user, and, in particular, to a patient interface device having a structure that includes controlled flexing and auto-adjustment of a cushion relative to a frame.
2. Description of the Related Art
There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube in their esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver continuous positive airway pressure (CPAP) or variable airway pressure, which varies with the patient's respiratory cycle, to treat a medical disorder, such as sleep apnea syndrome, in particular, obstructive sleep apnea (OSA), or congestive heart failure.
Non-invasive ventilation and pressure support therapies involve the placement of a patient interface device including a mask component on the face of a patient. The mask component may be, without limitation, a nasal mask that covers the patient's nose, a nasal cushion having nasal prongs that are received within the patient's nares, a nasal/oral mask that covers the nose and mouth, or a full face mask that covers the patient's face. The patient interface device interfaces the ventilator or pressure support device with the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient. It is known to maintain such devices on the face of a wearer by a headgear having one or more straps adapted to fit over/around the patient's head.
Patients that that require pressure support therapy are often confronted with the problem of finding a suitable patient interface device. In finding a suitable patient interface device, such patients frequently struggle with issues relating to the seal and stability of the patient interface device, the comfort of the patient interface device, the size/weight of the patient interface device, and the sizing of the patient interface device. These challenges, if not addressed properly, can compromise the patient's compliance with the prescribed therapy.
More specifically, during the night, the stability of a mask seal will be challenged by the patient moving about in his or her bed. The changing head position can lead to air delivery hose torque and general interference with other objects (e.g. pillows, sheets, blankets, etc.). Thus, stability, and consequently seal, is a challenge for any patient interface device in the market.
In addition, patient comfort is an important factor, and can be negatively impacted in many ways. For example, over-tightening of the headgear (to compensate for lack of seal and stability) can increase pressure on the face and head, which in turn can result in pressure points and/or skin breakdown. Other components of the patient interface device (e.g. straps, frames, headgear, etc.) can also add discomfort for the patient because the geometry of such components can conflict with facial structures.
Furthermore, the general weight of the patient interface device can negatively impact a patient's experience by causing additional facial pressure or compounding over-tightening issues. Patient interface device weight can also negatively affect the seal and stability. Certain patients also have problems with a patient interface device interfering with his or her line of sight, and overall patient interface device size has been known to cause claustrophobia is some patients.
Finally, properly sizing a patient interface device can be difficult because facial structures vary greatly among patients. Not all patient interface devices are able to accommodate this range of differences, thus requiring either more sizes/variations or not providing an optimal fit for the majority of the user population.